Monday, February 26, 2007


phylum Platyhelminthes
Flatworms lack circulatory or respiratory systems because they are so flat. Therefore, Oxygen and nutrients are transported to other tissue cells by diffusion. And flatworms also get rid of carbon dioxide and metabolic wastes by diffusion.

Freshwater flatworms such as planarians have structures called flame cells that help them get rid of water as they form a network that empties through tiny pores in the animals’ skin.

phylum Nematoda
Roundworms also lack respiratory and circulatory system. They transport nutrients, collect oxygen and get rid of metabolic waste by diffusion through their bodies.

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